Oriented to the 3 dimensional process design requirement for deformed parts of small arms, and focusing on the special processes, such as stamping, extension and so on, this paper puts forward a “CAD+DEFORM-based” three-dimension process design method, and at the same time, it elaborates the concrete implementation scheme of this method. Based on this, taking a certain cartridge of small arms for an example, it expounds on its application method and efficiency. The result show that, the method can effectively improve the development efficiency and quality of light weapon products, meeting the design and application of special process in the deformation parts, which provides the effective technical support to achieve the integrated design and manufacturing of the full 3 dimensional small arms.